Pulsating syringe

ABSTRACT

A hydraulic oscillator which produces a pulsed output from a steady flow input. The oscillator utilizes a rigid pressure chamber containing a charge of gas under pressure. A conduit passes through this chamber, and the conduit includes an inlet passage, an outlet passage and, interconnecting and extending between these passages, a flexible, resilient, collapsible-walled tubular portion. The outside of this portion is fully peripherally exposed to gas pressure in the chamber. When the impedance and resistance to liquid flow through the inlet and outlet passages, the elasticity and dimensions of the tubular portion, and the gas pressure in the chamber, are appropriately selected, then a liquid stream entering the inlet passage at a suitable pressure relative to the chamber pressure, will emerge as a pulsating flow. This pulsating flow is particularly suited to many purposes, including the cleaning, irrigating and massaging of biological living tissue, the creation of cavitation in a flowing stream, and the momentary and cyclical reversal of the direction of flow in a generally forwardly flowing system. Systems for utilizing this oscillator for these purposes are disclosed.

United States Patent [191 Lambert May 14,1974

Primary Examiner-L. W. Trapp Attorney, Agent, or Firm-Donald D. Mon

[57] ABSTRACT A hydraulic oscillator which produces a pulsed output froma steady flow input. The oscillator utilizes a rigid pressure chambercontaining a charge of gas under pressure. A conduit passes through thischamber, and the conduit includes an inlet passage, an outlet passageand, interconnecting and extending between these passages, a flexible,resilient, collapsible-walled tubular portion. The outside of thisportion is fully peripherally exposed to gas pressure in the chamber.

When the impedance and resistance to liquid flow through the inlet andoutlet passages, the elasticity and dimensions of the tubular portion,and the gas pressure in the chamber, are appropriately selected, then aliquid stream entering the inlet passage at a suitable pressure relativeto the chamber pressure, will emerge as a pulsating flow. This pulsatingflow is particularly suited to many purposes, including the cleaning,irrigating and massaging of biological living tissue, the creation ofcavitation in a flowing stream, and the momentary and cyclical reversalof the direction of flow in a generally forwardly flowing system.Systems for utilizing this oscillator for these lJlIPOSfiS aredisclosed.

13 Claims, 7 DrawingFigures PULSATING SYRINGE CROSS-REFERENCE TO OTHERPATENT APPLICATIONS This application is a continuation-in-part ofapplicants abandoned copending U.S. Pat. application, Ser. No. 1 10,094filed Jan. 27, I97 I entitled Oral Hygiene Device, which was abandonedupon the filing of this instant application.

This invention relates to a hydraulic oscillator which converts asteady-flow stream of water into a pulsating stream, without the use ofmoving parts as that term is commonly used. It also relates to a systemfor providing a pulsating liquid flow of unique properties for variouspurposes, including the irrigation, cleansing or massaging of biologicaltissue.

One disadvantage of existing devices for this function resides in theirusage of various classes of motors, pumps, and precision parts in orderto create the pulsating flow, and in the resulting high cost andshortterm functional life of the device. I

Still another disadvantage of prior art devices for producing pulsedstreams for cleansing biological tissues resides in what occurs if theoutlet nozzle is fully or partially occluded. If the device is aconstantdisplacement type, as many are, then the pressure of the streamwill rise as high as necessary in order to overcome the obstacle andeject the liquid (subject, of course, to stalling out or breakingfirst). Partial occlusion of the exhaust orifice decreases itscross-section, and causes the pressure to rise and the stream toaccelerate. This would occur in the case of the partial occlusion whichwould result when the high pressure partially unblocked the orifice, orin which the orifice was brought close to a blocking surface. In bothevents, an undesirably strong, small jet of fluid results, which canseverely abrade and damage the tissue.

A similar result occurs when an orifice discharging from a steady statestream carried from a water source such as a faucet is partially ortotally blocked. While the pressure itself will build no higher thanthat of the source, the velocity of the effluent stream will increasepartially, and may do damage to the tissue.

In contrast, the partial occlusion of the outlet stream of thisinvention actually causes the system to throttle down to a mere dribble.There is no risk of damage to the tissues, because there is no jettingstream. Accordingly, a pulsating jet stream can be directed at the mostsensitiveof tissues, without caution for the placement of the nozzle, inthe sure and certain knowledge that no jet stream will issue except atsafe velocities and pressures. Thus,-the oscillator according to thisinvention enables to be made a new pulsating-jet system with completelydifferent output characteristics from those which have heretofore beenknown.

Another disadvantage of prior art pulsating jet systems resides in thefact that they cannot *tailor" the shape and volume of the globules ofthe jet stream. In accordance with this invention, while stillmaintaining the same frequency (which itself is selectible), one canvary the liquid content (volume) and shape (length and cross-section) ofthe globules so as to impinge upon a surface a stream of globules of ashape which can opti-- mally treat the surface.

Another object ot this invention is to produce, when desired a momentaryand cyclical reversal of the direction of flow in generallyforwardly-flowing stream. This enables elements such as filters to becontinuously backwashed. This is only one of many potential uses of thisfeature. v

Still another object of this invention is to produce, if desired,cavitation in the outlet stream. There are many potential uses, besidesthat of study of the phenomenon, of considerable value.

A hydraulic oscillator according to this invention includes a rigidpressure chamber containing a charge of gas under pressure. A conduitpassing through and extending beyond the chamber has an inlet passage,an outlet passage, and between and interconnecting these two passages,and physically attached thereto, a deflectible resilient-walled-tubularportion whose outside wall is fully peripherally exposed, to the saidgas pressure in the pressure chamberqThe pressure of the gas charge isrelated to the pressure of the liquid in the inlet passage, such thatthe-liquid is driven out of thedevice at a velocity faster than itenters, and as a result, the fluid stream is broken up corpuscularly,resulting in a pulsating flow of timed, spaced-apart drops of water. Theimpedance and resistance to liquid flow through the inlet and outletpassages, the elasticity and dimensions of the tubular portion, and thegas pressure in the chamber, are selected such that apulsating flow iscreated at the exit from the outlet passage.

A tissue-treating system according to this invention utilizes theforegoing oscillator in combination with a source of liquid underpressure connected to the inlet passage by a supply tube.

According to a preferred but optional feature of this invention, theproperties of the source other than its pressure output, aresubstantially dynamically isolated from the tubular portion, wherebywaves set up by the tubular portions contortions do not deleteriouslyinteract with the properties of the pressure source.

The above and other features of this invention will be fully understoodfrom the following detailed description and the accompanying drawings,in which:

FIG. I is an axial cross-section, partly in schematic notation, showingthe presently preferred embodiment of the invention; I

FIG. 2 is a cross-section taken at line 22 of FIG. I;

FIG. 3 is a fragmentary axial cross-section schematically showing somefacets of the operation of the device in FIG. 1;

FIG. 4 is a graph illustrating some features operation of the system;

FIG. 5 is a schematic elevation of another embodiment of the invention;

FIG. 6 is an enlarged portion of FIG. 5, partly in axial cross-section;and

FIG. 7 is a fragmentary schematic view of an accessory which mayoptionally be used with this invention.

at the End plates 14 and 15 include shoulders 19, re-

spectively, inside the pressure chamber. A tubular portion 21 isattached to these two shoulders inside the pressure chamber. It isspaced from the wall of the chamber, and is fully peripherally exposedto its pressure.

A band 210 binds the tubular portion to the shoulder on the upstream endplate. The downstream end of the tubular portion is stretched over theshoulder of the downstream end plate, but not bound thereto. The tubularportion is deflectible and resilient, and its relaxed inner diameter issmaller than the outer diameter of both of the shoulders. The springbackforce of the tubular portion will be sufficient to maintain a seal undernormal operating conditions, but it is preferable for the upstream endto be bound, such as by band 21a, because the pulsating forces at theupstream end may deflect the tube enough to cause leakage under certainconditions at that end.

At the time of manufacture, gas can be forced into the tubular portionunder sufficient pressure to overcome the unbound seal, thereby tostretch that end of the tubular portion and leak past it into thepressure chamber so as to charge the chamber to its desired pressurelevel. When this elevated pressure is relieved in the tubular portion,the seal is restored by the forces derived from the gas pressure in thepressure chamber and from the elastic springback of the material so asto keep the gas contained in the pressure chamber. Thus the downstreamend of the tubular portion acts as a valve to admit and to retainchamber pressure. The approximate pressure can be determined bymeasuring the water pressure required to open the tubular portion toflow after it has been collapsed by the gas pressure.

The tubular portion, being flexible, and resilient, is deflectible inthe sense of being collapsible. The term collapsible" does notnecessarily mean collapsed flat so as completely to close the tubularportion, although it includes this condition. It means that the tubularportion has relatively little resistance to bending, being relativelythin or relatively soft, so it can buckle, bend, pinch, and undergo likecontortions. Without fluid pressure inside the tubular portion of avalue somewhat above that of the chamber pressure, the gas pressure inthe chamber will tend to close it. Sufficient pressure inside thetubular portion tends to open the tube, thereby to permit liquid to flowthrough it. The dimensional and pressure relationships discussed belowwill result in a cyclical increase and decrease in lateral cross-sectionarea along the length of the tubular portion. A fluctuation in liquidflow will be generated as a consequence of the contortions of thetubular portion when liquid at a correct pressure relative to the gaspressure flows through the tubular portion, when the remainder of thesystem is also properly proportioned.

The tubular portion separates the gas in the chamber from the liquid inthe tubular portion, thereby allowing the gas pressure to be exerted onthe liquid, but without mixing them.

An upstream pressure compensating orifice 22 is formed in an orificeplate 23 adjacent to the water supply 24, which supply might be such asa faucet, a tank or a pump. This orifice enables a given system at agiven gas pressure to be used with a wide range of water systempressures, still producing the desired pulsating output.

The water supply is sometimes referred to as a pressure source. The terminlet passage means the passageway extending from the source of pressureto the end of port 16 facing into the tubular portion. In FIG. 1, thisincludes the bore 16 in the metal end fitting closest to the supply plusthe lumen of the hose to its junction with orifice plate 23. The termoutlet passage" means the passageway extending from end of the bore 17in the metal end fitting farther from the supply, plus the lumen of adischarge tip 27. Thus these terms comprehend the passageways which feedand discharge from the tubular portion. The inlet and outlet passagesplus the tubular portion are sometimes referred to as a conduit."

A discharge tip 27 bounds the downstream end of passage 20. In orderthat it may readily be removed and attached, this tip has a taper 28 onone end adapted to enter a matching taper 29 in the passage. Two O-rings30, 31 are seated in respective grooves 32, 33 in the wall of thepassage, and a shoulder 34 on the tip is adapted to pass beyond O-ring30 to aid in retention. The force generated by pressing taper 28 againstthe O-rings also retains the tip. The tip has a delivery tube 35 whichterminates at adischarge nozzle 36.

The fluttering tube effect utilized herein is relatively unknown at thepresent time. However, reference may be made to the following referencesfor some details concerning it, even though many of these details areincorrect, misleading, and insufficient to guide one to the means forsecuring the objectives of this invention.

Rodbard, S. and Saiki, H.: Flow-through Collapsible Tubes, AmericanHeart Journal 46: 7.15, 1953 and Lambert, J.W Flutter from SteadyDriving Pressures: Elementary Theory, Proceedings of the AmericanSociety of Civil Engineers, Engineering Mechanics Division Meeting,Washington, DC, Oct. 13, 1966.

IBM Technical Disclosure Bulletin, Vol. 13 No. 5, October 1970, entitledSonar Sound Generator" by LJ. Andrews and J.W. Lambert.

Briefly stated, with the pressure relationships stated above, namelywith chamber pressure below that of the pressure at the inlet passage,the fluttering tube accelerates the water such that its linear exitvelocity is greater than it linear inlet velocity. The tendency is toempty the device faster than it can be filled, and as a result the flowbecomes corpuscular, the tubular portion changing its lateralcross-section area in the process. In fact, it may even close betweendrops, and open to permit the flow of a drop. With some relationships ofpressures and dimensions, the stream may not become a succession ofseparate drops, but instead one of a continuous stream with anundulating cross-section. With some other relationships the flow in theoutlet passage reverses, and in others, some part of it cavitates.

FIG. 3 schematically shows the general mode of operation of the flexibletubular portion. Without liquid pressure in the tubular portion, itcollapses and constricts, sometimes closing nearly completely. Whensufficient liquid pressure is exerted to open the tubular portionagainst the gas pressure, a peculiar wave motion begins to occur in thewall of the tube. Essentially, it involves a progression of waves, whichcan be the alternating filling and emptying the tubular portion, withwaves traveling back and forth along the tubular portion. The tubularportion is shown at one of its instantaneous positions in FIG. 3, theportion tapering inwardly from the inlet and to a point 50 where it isalmost closed. Then it tapers outwardly again to the discharge end. Insegment 51, there is a breathing motion shown by the two sets of dashedlines, and in segment 52, another similarly shown breathing motion.

It appears that there is a pulsating flow in segment 51 which forcesliquid past point 50 at its peak, and is retarded at point 50 by closureor near closure of the tube at that point at lower pulse pressures.However, seg ment 52 accelerates the corpuscle of liquid ,which passedpoint 50 before it closed down, and the discrete drop appears to form inthis region. The inertia of the drops, and the' continuing pressurepulses cause the stream to discharge co'rpuscularly.

It is a feature of this oscillator system, that if the discharge orificeis partially occluded, the velocity of the output pulses of liquid isdiminished. With sufficient occlusion, oscillation stops and the systemreverts to a steady, very low velocity flow. This low velocity is muchless than would be the velocity created by the same pressure source andconduitry without the choking effect of the tubular portion.

The basis for this safety factor will be understood from a study of FIG.4, which is a graph which plots as the abscissa the location along thesystem of the elements, and as an ordinate, the static pressure measuredat points along the system while the system is flowing. If the system isplugged and flow stops, then of course all points rise to the sourcepressure.

There is a source pressure 65 feeding through the inlet passage to thechamber, shown as element 66 in FIG. 4. There is a critical chamberpressure 67, (Per). This critical pressure is ideally the fluid staticpressure within the portion at steady flow. This would be measured bystarting flow of liquid through the system without any pressure-in thechamber, and gradually building up the chamber pressure untiloscillation started. That pressure when it started is P Oscillation willoccur at all chamber pressures higher than P,., and. lower than P Therange R above this level represents chamber pressures, P at whichoscillation will occur. Point 68 represents an outlet pressure such asatmosphere. it will be raised by occlusion, and point 69 shows one suchlevel, which occurs as a consequence of partial occlusion. Now noticethat the differential pressure driving liquid into the oscillator isonly P, P, (supply pressure minus chamber pressure), and this is verysmall.

Further the pressure difference l P which is much diminished from P, Pdue to the occlusion is the only pressure available for acceleration (ifany) and hence with occlusion, high, jetting,,exit velocities cannotoccur. With complete occlusion the entire system of course reverts to asteady source pressure with the occluding force limited to sourcepressure times the small area of the discharge orifice, but the staticpressure atthe opening will not abrade, because there is no flow. Thisis demonstrated in FIG. 4.

For biological cleansing purposes the chamber pressure will be setrelatively close to inlet pressure, thereby:

l. Causing a relatively low rate of inlet flow to the oscillator;

2. Causing a relatively large pressure drop for acceleration ofcleansing drops; and

3. Limiting the flow in case of partial occlusion of the discharge.

One of the problems inherent in previous attempts to make hydraulicoscillators of this type has been that oscillation has either beenimpeded, totally frustrated, or the output rendered unstable and impurein wave-form by inter-reaction between the pressure source and thetubular portion. Some efforts have been made to over come this problem,but without significant success, and definitely without a solution tothe problem which would enable an oscillator to be made which does havea pure output of desired wave-form characteristics and which willcontinue to oscillate steadily. Similarly, other design characteristicswere unknown which could have assisted in the design.

Primarily, a pure output in the sense of a steady-state ocillation ofpulses of uniform shape, is derived from'a substantially steady flowrate to the tubular portion.

This requires much more than just a non-pulsing source, because thepressure pulsations of the tubular portion can, unless isolation isprovided for the supply from the tubular portion, so effect the inputstream that it has fluctuations in its flow rate, and these interferewith the frequency of the tubular portion, and the behavior of thesystem becomes variable from cycle to cycle,-a situation which is bothunmanageable and unpredictable.

It has been found that the problems derived from the source are solvedby providing a sufficiently high impedance to flow upstream of thetubular portion. The dimensions of impedance are:

length/cross-section area L/A of the supply tube.

It has been found that by providing the inlet passage with an impedanceat least 5- times as great as that of the discharge passage, the inletstream entering the tubular portion will be relatively free of suchwave-forms from the tubular portion as will frustrate the properoscillation of the system. Greater ratios may of course be used, and insystems where priority of output is of no importance, but other featuresare, the ratio might even be less than one. There are pressurevariations in the tubular portion at its end adjacent to the inletpassage. If the impedance of the inlet passage is great enough, thesedownstream fluctuations will have no significant effect on the steadyrate of flow of the liquid into the tubular portion.

The resistance of the inlet passage is of importance because, over awide range .of supply pressures, it limits the range of streamvelocities, and thereby reduces frequency range with varying supplypressures; Orifice plate 22 performs that function. Similarly, theresistance of the inlet passage inter-acts with the pressure differenceP, P to establish the average flow rate, which in turn affects the timesand t;, in the equations below.

Some additional design considerations of this system are as follows:

OUTPUT FREQUENCY The frequency,f, is more easily discussed in terms ofthe period T of one cycle which is l f. The period of t is the timerequired to accelerate the liquid in the discharge line a certainamount. This time is a function of the pressure difference between thechamber and the outlet, and the impedance (L/A) of the outlet passage.The actual formula for 1 is the solution of a complex nonlineardifferential equation, and also involves the elastic properties of theflexible tube.

Times t and t;; are associated with the times required for two differentwaves to traverse the flexible tube. One of these waves is anaccelerating velocity wave in the collapsed portion of the tube, and theother is a decelerating velocity wave in the collapsed portion of thetube. The time of propagation of each of these waves is related to thelocal fluid velocity within the flexible tube. Thus the designparameters controlling t and 1 are the inlet pressure difference (P Pthe inlet passage resistance, and indirectly the outlet passageresistance.

Thus in selecting frequencies, if t is large compared to t and ifrequency can be selectibly controlled by chamber pressure and by thelength of the discharge pipe. On the other hand if 1 and t are largercompared to t, frequency can be selectibly controlled by varying inletpipe length, source pressure and/or chamber pressure.

As general statements, the given set up:

a. An increase in F increases the frequency if I is large compared toboth of t and b. An increase in length of the outlet passage decreasesthe frequency;

c. An increase in inlet passage length decreases the frequency;

d. An increase in P (source pressure) increases the frequency; and

e. An increase in chamber pressure decreases the frequency if and areboth large compared to t,

DROP SHAPE AND VOLUME The gross size of each drop is primarilydetermined by the general plumbing, and by the frequency generated.

.The shape of the drops can be varied by changing either the chamberpressure or the inlet pressure to the tubular portion.

One example of dimensions for an oral hygiene device, which, at a supplypressure upstream of orifice 22 between about 75 psig to I20 psig willproduce a pulsating stream pulsating at about 20 cycles per second, isas follows:

Gas pressure (nitrogen or other inert gas) in the chamber 58 psig.

Upstream passage l6: 3 inches in length, inner diameter: 0.06 inches.

Downstream passage 17 plus conduit 35 in tip 27: 4 inches in length,inner diameter: 0.06 inches.

Orifice 22: 0.040 inches diameter.

Tubular portion 21: Unsupported length: l5/l6 inches; wall thicknessabout l/l6'inches; relaxed inner diameter: 3/l6 inches; preferredmaterial; neoprene rubber or silastic (silicone) rubber. Further as tothe material for tubular portion 21, it appears that an elastomericproperty is to be sought. The elasticity of the portion appears toaffect the frequency, and of course the material must be flexible, andthe neoprene and silastic rubbers would be selected from those of thesetypes which have the extensibility and return to original length typicalof elastomers.

Shoulders 19, Diameter: 3/8 inches.

following pertain for a Discharge nozzle 36: Diameter: 0.040 inches;length: 1/4 inches.

FIG. 5 shows another system for washing biological tissue. This systemis a douche. It has a tank which drains into a hose (inlet passage) 71.An off-on valve 72 of any desired type is located in the hose. A nozzle(outlet passage) 73 has ports 74 to discharge a pulsating stream.

An oscillator 75 is connected to the inlet passage and outlet passage.It includes a rigid case 76 with a pressure chamber 77 in which acollapsible tubular portion 78 of flexible material is enclosed. ltinterconnects the inlet and outlet passages. The tubular portion andpassages are together sometimes referred to as a conduit. In theillustrated embodiments, and generally with the usage of this invention,the conduit will be cylindrical, sometimes with steps between adjacentdifferent diameters.

This system, properly proportioned and charged with gas, will produce apulsating output ofwater. The maximum inlet pressure is limited by thelength of the hose, because this limits the elevation of the'water bagrelative to the oscillator. The system will oscillate when there is apressure head above the oscillator of at least eleven inches of water.

As an example of a workable system, the following details are given:

L (length of inlet passage) 4 feet D, A inch inside diameter L (lengthof outlet passage) about 4- /2 inches,

eight or nine outlet ports, totaling area of A inch diameter circle D A1inch inside diameter L unsupported length of tubular portion, l-A inchesD A inches inside diameter W relaxed wall thickness 0.012 inch.

Total length of tubular portion in relaxed state about 2 inches.

Chamber pressure, about 0.37 psig.

The hose forming the inlet passage is semi-rigid plastic hose. Theoutlet tip is a hard plastic.

The material of the tubular portion is latex rubber with a modulus ofelasticity of about 100 psi.

A two quart tank will empty in about 90 seconds, the frequency ofoscillation being about twenty cycles (pulses) per second.

There will be applications wherein it is desirable to have a pulsatingflow somewhere in a system, but it will be necessary to remove thepulsations and return the stream to an unpulsed flow, without goingthrough a sump. For this purpose, and as shown in FIG. 7, the outletpassage 80 from any of the aforementioned system may be passed by aHelmholtz resonator 81. A typical example is a pressure dome having achamber 82 with a flexible diaphragm 83 extending across it. Gas underpressure is charged into the top of the chamber, and fluctuations in thestream are absorbed by this device.

As to the interdependence of the various proportions, dimensions, andproperties of materials, some experimentation must be anticipated,because knowledge of this phenomenon is at present very incomplete.However, by starting with the considerations, materials and dimensionsgiven above, one can, without undue experimentation, scale'the device toother sizes'and frequencies.

in summary, by appropriate selection of the impedances and resistancesofthe inlet an outlet passages, of the dimensions and modulus ofelasticity of the tubular portion, and of the supply and chamberpressures, one can arrange for various kinds of pulsed outputs. Theimpedances of the inlet and outlet passages are of importance because oftheir effects on the capacity of the tubular portion to receive andexpel liquid from the system. The impedance of the inlet passage servesdynamically to isolate the tubular portion fromthe supply so they do notaffect each other.

The dynamic impedance of the outlet passage is important as tofrequency, drop shape, drop volume, and the phase relationships betweenpressure levels within a single cycle. With appropriate relativeselection of outlet impedance, there can even be a reversal of flow inthe outlet passage between drops. This is an ideal relationship for anoral hygiene device, because the drops are so sharply separated, andalso is ideal for backwash systems wherein cyclical reverse flow in agenerally forwardly moving stream is desirable. This reversal of flowwill be found to occur principally when the unstressed diameter of thetubular portion is larger than the diameter of both the inlet passageand the outlet passage.

Similarly, cavitation can be induced, which will in these systemsprovide a laboratory tool for the study of the effects of cavitation ina traveling stream, and can provide for mixing and vaporization ofvaporizable mixtures such as liquid fuels.

Further, this oscillator can be used as a ditherer to keep a streamlive, and to exert mechanical forces which can overcome stick-sliptendencies, in associated mechanical systems. v

This oscillator will function with any liquid, and while its principalusage is expected to be with water, it can also be used for milk, oils,fuels, solvents, and other liquids in general, wherever an oscillatingflow is desired.

, but only in accordance with the scope of the appended claims.

I claim:

l. A hydraulic oscillator for discharging fluid onto living biologicaltissue, said oscillator producing a pulsating fluid output stream from asteady inlet flow, said oscillator having the property of producing onlya relatively sluggish output stream when its outlet is partiallyoccluded, said oscillator comprising: a rigid pressure chamber; a chargeof gas contained in said chamber; a conduit passing through and beyondsaid chamber, said conduit comprising an inlet passage, an outletpassage, said passages having the properties of impedance and resistanceto liquid flow, and a flexible, collapsiblewalled tubular portionextending between and interconnecting said passages, that part of thetubular portion which extends between the passages having an outsidewall which is fully peripherally exposed to the gas in the chamber, theinlet passage being adapted for connection to a source of liquid undersupplypressure, the pressure of the chamber being above thatcriticallevel at and above which oscillation will always occur, and less thanthe pressure of the source, and the resistance and dynamic impedance ofthe outlet passage being such as to secure a cyclical output. 2. Ahydraulic oscillator according to claim 1' in which the chamber pressureand the supply pressure are selected to be sufficiently close to eachother in magnitude that, when the outlet passage is partially occluded,flowthrough the .system occurs at a relatively small rate as aconsequence of the relatively small difference between the said twopressures.

3. In a system for discharging fluid onto living biological tissue, saidsystem having a supply of fluid under steady supply'pressure, and anoutlet tip to direct an output stream, a hydraulic oscillator causingsaid output stream to pulsate, and having the property of producing onlya relatively sluggish output stream when its outlet is partiallyoccluded, said oscillator comprising: a rigid pressure chamber; a chargeof gas contained-in said chamber; a conduit passing through and beyondsaid chamber, said conduit comprising an inlet passage, an outletpassage, said passages having the properties of impedance and resistanceto liquid flow, and a flexi ble, collapsible-walled tubular portionextending between and interconnecting said passages, that part of thetubular portion which extends between the passages having an outsidewall which is fully peripherally exposed to the gas in the chamber, theinlet passage being adapted for connection to a source of liquid undersupply pressure, the pressure of the chamber being above that criticallevel at and above which oscil lation will always occur, and less thanthe pressure of the source, and the resistance and dynamic impedance ofthe outlet passage being such as to secure a cyclical output.

4. Apparatus according to claim 3 in which the chamber pressure and thesupply pressure are selected to be sufficiently close to each other inmagnitude that, when the outlet passage is partially occluded,flowthrough the system occurs at a relatively small rate as aconsequence of the relatively small difference between the said twopressures.

5. A system for generating and discharging a pulsing flow of liquid uponliving biological tissue comprising:

a supply source of liquid under pressure; an outlet tip' for directingthe flow to a selected location; and a hydraulic oscillator comprisingrarigid pressure chamber; a charge of gas contained in said chamber; aconduit passing through and beyond said chamber, said conduit comprisingan inlet passage, an outlet passage, said passages having the propertiesof impedance and resistance to liquid flow, and a flexible,collapsible-walled tubular portion 'extending between andinterconnecting said passages, that part of the tubular portion whichextends between the passages having an outside wall which is fullyperipherally exposed to the gas in the chamber, the inlet passage beingadapted for connection to a source of liquid under supply pressure,being sufficiently large so as substantially to isolate the tubularportion dynamically from the pressure source, the pressure of thechamber being above that critical level at and above which oscillationwill always occur, and less than the pressure of the source, and theresistance and dynamic impedance of the outlet passage being such as tosecure a cyclical output, the inlet passage being connected to thesupply source, and the outlet passage discharging through the tip.

6. A system according to claim in which the chamber pressure and thesupply pressure are selected to be sufficiently close to each other inmagnitude that, when the outlet passage is partially occluded,flowthrough the system occurs at a relatively small rate as aconsequence of the relatively small difi'erence between the said twopressures.

7. A system according to claim 5 in which the tip is adapted for use asan oral hygiene device.

8. A system according to claim 5 in which the tubular portion is made ofan elastomeric material.

9. A system according to claim 5 in which the inlet and outlet passagesterminate at shoulders located inside the pressure chamber, over whichshoulders the tubular portion is stretched, at least one end of thetubular portion being held to the respective shoulder only by thespringback force of the material of the tubular portion, whereby gas maybe injected into the pressure chamber by exerting sufficient forceinside the tubular portion to cause the gas to leak past that shoulder.

10. A system according to claim 9 in which the tubular portion is madeof an elastomeric material.

11. A system according to claim 5 in which the inner diameters of thepassages are smaller than the inner diameter of the tubular portion inits relaxed condition.

12. A system according to claim 11 in which the inlet and outletpassages terminate at shoulders located inside the pressure chamber,over which shoulder the tubular portion is stretched, at least one endof the tubular portion being held to the respective shoulder only by thespringback force of the material of the tubular portion, whereby gas maybe injected into the pressure chamber by exerting sufficient forceinside the tubular portion to cause the gas to leak past the shoulder.

13. A system according to claim 11 in which an orifice is placed in theflow of the liquid stream upstream of the inlet passage.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,810,465 Dated May 14, 1974 Inventor(s) JOHN W. LAMBERT It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

[76], line 2 "91714" should read "91740-- Abstract, line 6 after "safirst occurrence, insert a comma Col. line 2 'source,'" s Eould read--source". Col. 4, line 14 'conduit."' should read --"conduit".-- Col.4, line 45 "it" should read -its- Q Cole 5, line 28 "while the system isflowing" should be under ined Col. 5, line 50 "P should read --P Col. 6,line 15 "ocillation" should read --oscillation- Col. 8, line 15 'duit."'should read --duit".-- Col. 8, line 54 "tem" should read --tems-- Col.9, line 31 "'live,"' should read --"live",--

C010 10, line 11 "flowthrough" should read --flow through-- ((11. 2,line 5) Col. 10, line L- :41 "flowthrough" should read --flow through--(c1. 4, line 4 Col. 11, line 6 "flowthrough" should read --flowthrough-- 0 (c1. 6, line 4 Signed and Scaled this Eighth Day of March1977 [SEAL] Arrest:

RUTI'I C. MASON C. MARSHALL DANN Amfling Office Commissioner of Parentsand Trademarks

1. A hydraulic oscillator for discharging fluid onto living biologicaltissue, said oscillator producing a pulsating fluid output stream from asteady inlet flow, said oscillator having the property of producing onlya relatively sluggish output stream when its outlet is partiallyoccluded, said oscillator comprising: a rigid pressure chamber; a chargeof gas contained in said chamber; a conduit passing through and beyondsaid chamber, saId conduit comprising an inlet passage, an outletpassage, said passages having the properties of impedance and resistanceto liquid flow, and a flexible, collapsible-walled tubular portionextending between and interconnecting said passages, that part of thetubular portion which extends between the passages having an outsidewall which is fully peripherally exposed to the gas in the chamber, theinlet passage being adapted for connection to a source of liquid undersupply pressure, the pressure of the chamber being above that criticallevel at and above which oscillation will always occur, and less thanthe pressure of the source, and the resistance and dynamic impedance ofthe outlet passage being such as to secure a cyclical output.
 2. Ahydraulic oscillator according to claim 1 in which the chamber pressureand the supply pressure are selected to be sufficiently close to eachother in magnitude that, when the outlet passage is partially occluded,flow-through the system occurs at a relatively small rate as aconsequence of the relatively small difference between the said twopressures.
 3. In a system for discharging fluid onto living biologicaltissue, said system having a supply of fluid under steady supplypressure, and an outlet tip to direct an output stream, a hydraulicoscillator causing said output stream to pulsate, and having theproperty of producing only a relatively sluggish output stream when itsoutlet is partially occluded, said oscillator comprising: a rigidpressure chamber; a charge of gas contained in said chamber; a conduitpassing through and beyond said chamber, said conduit comprising aninlet passage, an outlet passage, said passages having the properties ofimpedance and resistance to liquid flow, and a flexible,collapsible-walled tubular portion extending between and interconnectingsaid passages, that part of the tubular portion which extends betweenthe passages having an outside wall which is fully peripherally exposedto the gas in the chamber, the inlet passage being adapted forconnection to a source of liquid under supply pressure, the pressure ofthe chamber being above that critical level at and above whichoscillation will always occur, and less than the pressure of the source,and the resistance and dynamic impedance of the outlet passage beingsuch as to secure a cyclical output.
 4. Apparatus according to claim 3in which the chamber pressure and the supply pressure are selected to besufficiently close to each other in magnitude that, when the outletpassage is partially occluded, flow-through the system occurs at arelatively small rate as a consequence of the relatively smalldifference between the said two pressures.
 5. A system for generatingand discharging a pulsing flow of liquid upon living biological tissuecomprising: a supply source of liquid under pressure; an outlet tip fordirecting the flow to a selected location; and a hydraulic oscillatorcomprising: a rigid pressure chamber; a charge of gas contained in saidchamber; a conduit passing through and beyond said chamber, said conduitcomprising an inlet passage, an outlet passage, said passages having theproperties of impedance and resistance to liquid flow, and a flexible,collapsible-walled tubular portion extending between and interconnectingsaid passages, that part of the tubular portion which extends betweenthe passages having an outside wall which is fully peripherally exposedto the gas in the chamber, the inlet passage being adapted forconnection to a source of liquid under supply pressure, beingsufficiently large so as substantially to isolate the tubular portiondynamically from the pressure source, the pressure of the chamber beingabove that critical level at and above which oscillation will alwaysoccur, and less than the pressure of the source, and the resistance anddynamic impedance of the outlet passage being such as to secure acyclical output, the inlet passage being connected to the supply source,and the outlet passage discharging throuGh the tip.
 6. A systemaccording to claim 5 in which the chamber pressure and the supplypressure are selected to be sufficiently close to each other inmagnitude that, when the outlet passage is partially occluded,flow-through the system occurs at a relatively small rate as aconsequence of the relatively small difference between the said twopressures.
 7. A system according to claim 5 in which the tip is adaptedfor use as an oral hygiene device.
 8. A system according to claim 5 inwhich the tubular portion is made of an elastomeric material.
 9. Asystem according to claim 5 in which the inlet and outlet passagesterminate at shoulders located inside the pressure chamber, over whichshoulders the tubular portion is stretched, at least one end of thetubular portion being held to the respective shoulder only by thespringback force of the material of the tubular portion, whereby gas maybe injected into the pressure chamber by exerting sufficient forceinside the tubular portion to cause the gas to leak past that shoulder.10. A system according to claim 9 in which the tubular portion is madeof an elastomeric material.
 11. A system according to claim 5 in whichthe inner diameters of the passages are smaller than the inner diameterof the tubular portion in its relaxed condition.
 12. A system accordingto claim 11 in which the inlet and outlet passages terminate atshoulders located inside the pressure chamber, over which shoulder thetubular portion is stretched, at least one end of the tubular portionbeing held to the respective shoulder only by the springback force ofthe material of the tubular portion, whereby gas may be injected intothe pressure chamber by exerting sufficient force inside the tubularportion to cause the gas to leak past the shoulder.
 13. A systemaccording to claim 11 in which an orifice is placed in the flow of theliquid stream upstream of the inlet passage.